9-16 1 PM Influenza

9-16 1 PM Influenza - Influenza virus Influenza history...

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Influenza virus
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Influenza history Historical records indicate flu-like epidemics throughout recorded history. Epidemics frequent but irregular. Sometimes disappear for a period of time. Variation in severity but usually cause mortality in elderly. Some appear to spread across Russia from Asia. Influenza virus isolated in 1933 Seroarcheology suggests antigenic variation Major pandemics in 1957, 1968, 1977 Frequent epidemics between pandemics Average annualized influenza associated excess morality in the US from 1979-2001 = 41,400 Bottom line: Influenza virus somehow manages to make frequent minor changes and sudden major changes which permit temporary evasion of a population's immunity. How?
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Influenza epidemiology in humans Fields Virology, 2nd ed, Fields & Knipe, eds, Raven Press, 1990, Fig.40-1
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Influenza mortality from 1957 to 1979 Fields Virology, 2nd ed, Fields & Knipe, eds, Raven Press, 1990, Fig.40-11
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Influenza classification Family orthomyxoviridae Three types: A, B, C Types distinguished by antigenic differences in matrix and nucleoprotein antigens. A is more pathogenic than B. C is not a big problem Type A undergoes infects humans, swine, horses, seals, mink, whales, birds. Primary reservoir is birds In birds, infection is mostly asymptomatic, virus can replicate in lungs and intestinal mucosa; shed in feces Respiratory infection in humans Interspecies transmission. Influenza B and C are human viruses; do not infect birds.
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Influenza A reservoir Wild aquatic birds are the main reservoir of influenza A viruses. Virus transmission has been reported from weild waterfowl to poultry, sea mammals, pigs, horses, and humans. Viruses are also transmitted between pigs and humans, and from poultry to humans. Equine influenza viruses have recently been transmitted to dogs. (From Fields Vriology (2007) 5th edition, Knipe, DM & Howley, PM, eds, Wolters Kluwer/Lippincott Williams & Wilkins, Philadelphia, Fig 48.1)
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Electron micrographs of influenza virus. A–C: The structure of the internal components; (D) the external view. A substantial fraction (up to 50%) of influenza virions contain large helical internal components (A, B), which may contain individual ribonucleoprotein (RNP) segments (C) linked together. The individual RNPs each contain a binding site for the viral polymerase, as seen by the immunogold labeling of the end of the RNP segment (C). The external view of the virions (D) illustrates the pleomorphic appearance and the surface Influenza virus
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Structure of influenza virus. The diagram illustrates the main structural features of the virion. The surface of the particle contains three kinds of spike proteins: the hemagglutinin (HA), neuraminidase (NA), and matrix (M2) protein embedded in a lipid bilayer derived from the
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This note was uploaded on 07/30/2011 for the course MMC 6500 taught by Professor Gulig during the Spring '11 term at University of Florida.

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9-16 1 PM Influenza - Influenza virus Influenza history...

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